Art or process of manufacturing piston-rings



R. P. ELLIOTT.

ART ()8 PROCESS OF MANUFACTURING PISTON RINGS.

APPLICATION FILED FEB. 21. 1913.

1,386, 99'? Patented Aug. 9, 1921.

Invent UNIT D STATES PATENT- OFFICE.

RICHARD r. Eamon, or mxruqrolv, MASSACHUSETTS.

ART OR PROCESS OF MANUFACTURINGPISTON-RINGS.

Specification of Letters Patent.

Patented Aug. 9, 1921.

Application filed February 21, 1918. Serial No. 218,598. 1 I

My invention relates to an improvedmethod or process of manufacturingpiston rinse One of the objects of my HIVGDtlOIl is to provide a methodby whichrings of long wearing quality are produced.

A further object contemplates a method by which piston rings areproduced which give an even pressure at all points of their peripheryand do not tend to wear the cylinder of an engine out of a true circularform.

Other objects will be in part obvious and. in part pointed outhereinafter.

In the accompanying drawings, Figure 1 represents a rough casting of anindividual ring; Fig. 2 represents the slotting operation whereinprovision is made for allowing the ring to be contracted in order thatit may exert pressure against the walls of the coacting cylinder when inoperation; Fig. 3 represents an alternative form of slotting to thatshown in' Fig. 2-; Fig. 4.rep'resents a.

ring as compressed by a contracting device;

Fig. 5 represents a number of piston rings in the process of manufacturemounted upon an arbor to facilitate machining the outside surface of therings; Fig. 6 represents a number of piston rings in the process ofmanufacture in a fixture facilitating the machining of the inside of therings.

My improved method contemplates certain steps adapted to produceimproved piston rings and I have preferred to illustrate my invention asapplied to that form of piston ring wherein the rings are first castindividually .or separately and also to rings which have their insideand outside walls substantially parallel; it is to be understood,however, that my invention is not limited to the specific applicationherein shown but may be applied to rings which are first cast in thefamiliar pot form and cut up later into individual rings, or to ringswhich do not have their inside and outside walls substantially parallel.

Briefly described, my invention preferably contemplates eight stepsbeginning with a mug which has been cast individually, and the firstoperation is the removal of the inequalit es from the inner surface.From this polnt on the steps-which I prefer to fol low in practising mymethod, and'which will be more fully described hereinafter, are asfollows: Roughing and finishing the edges of the rings, slotting,contracting or closing-in and rough machining the outside diameter,allowlngthe rings toexpand to their normal condition, contractingagain'and machining the inside diameter while the rings are held 1ncontracted position, allowing them to ex 'pand for a second time,contracting again and completing the machining of the outside diameterwhile held in contracted position.

.After what may be termed a blank ring is produced either by casting thering separately or severing a ring from a pot casting, the first step inmy process contemplates the rough machining of the inside wall of thering indicated at 10, Fig. 1. The second step of my process-contemplatesthe rough machining of the edges or sides of the ring indicated at 11and 12, in such manner as to remove inequalities and some portions ofthe scale and bring the edges to a condition where they aresubstantially parallel, in the case of the individually cast ring. Thethird step in my process is the finish machiningv said surfaces 11 and12 to a smooth, level and substantially parallel relation, and to apredetermined thickness.

The fourthstep of my process involves the rough machining of the outsidediameter of the rings to remove the scale left by casting. In order topermit of high speed production, a number of rings, may be mounted upona fixture as indicated in Fig. 5, wherein an arbor or mandrel isrepresented at 13 having an enlarged body 14 and a shoulder 15 at oneend. The opposite end of the enlarged body is provided with a retainingflange 16 secured to the body member 14 by means of screws 17 or anyother suitable means so as to firmly clamp the rings in their closedcondition. It may be seen that such number of rings may be mounted onthe body 14 that they fill up the space between the shoulder 15 and theend 18 of the body 14, this body 14 being of such length as to insurethat the outer ring of the series, indicated at 19, will projectslightly beyond the end 18 so that when the plate or retaining member 16is drawn into operating position by means of the screws 17, the seriesof rings will be confined between the shoulder 15- and the member 16with sufficient pressure to hold them in their contracted condition.While thus mounted the outside of the rings are machined roughly andthey are then removed for the performance of the fifth step whichconsists in slotting the rings as indicated at 24c in Fig. 2 or 25inFig. 3, as may be desired.

The sixth'step of my process involves the use of the flexible closing-inor contracting device, indicated at 26, (Fig. 4) which forms the subjectmatter of United States Patent No. 1,258,664, granted to me March 12,1918. By the use of said device I am enabled to close-in or contract therings naturally and without subjecting them to undue local restraint, tothe condition shown in Fig. 4; they may now be again mounted upon thefixture shown in Fig. 5, the rings being maintained in contractedcondition by the flexible contracting device as set forth in saidpatent. When a sufficient number of rings have been mounted, the endplate 16 is secured to the body 14 by means of the screws 17 and whensaid screws have been tightened firmly,.the rings are confined betweenthe shoulder 15 and the end plate 16, the contracting fixtures may thenbe removed. While thus mounted and retained in contracted position theoutside diameters of the rings are machined approximately to finishedsize. At the close of this step the rings are dismounted and placed in afixture as indicated in Fig. 6, the inner bore of this fixture,indicated at 20, being truly circular, concentric with the axis of themachine upon which the fixture is mounted when it is desired to makeconcentric piston rings, and of the size to which the outside of therings were machined during the fifth step of my process. The fixtureshown in Fig. 6 is provided with a shoulder indicated at 21, and a plate22 is so arranged that when the screws 23 are tightened, the rings areheld firmly between the shoulder 21 and the plate 22. It will now beseen that the boring operation can be performed upon the inside diameterof the rings. This constitutes the seventh step and insures that theinside diameter of the rings will be a true circle when the rings areheld in contracted position, and also that the inside and outside Wallsof the rings shall be practically concentric when making the concentrictype of piston ringsi Upon the completion of the boring operation, .therings are removed and again contracted by means of my closing-indevice,before mentioned, and mounted a third time upon the fixture shown inFig. 5; whereupon" the eighth step, a final finishing operation,

is performed upon the outside of the rings, bringing them to theirpredetermined diameter and providing a smooth, round wearing surface.

It will be noted th: t the rings are allowed to expand and assume theirnatural position between the steps subsequent to the slotting operation,thus relieving all strains, and by the use of my contracting device therings are closed-in without undue local restraint, and any deformitiescaused by inequalities in the material, are thus provided for. Theresult of the various steps of my method is to produce, a piston ringfrom which all of the scale has been removed, unequal strainseliminated, and which will assume a truly circular form when closed-into operating position.

Piston rings which are made with their inside and outside wallssubstantially parallel are desirable because the rings may then be madeof sufficient size to fill up, in a great measure, the grooves in thepiston, thus preventing the leakage of oil and the accumulation ofcarbon in the piston ring grooves. It is desirable, furthermore, thatthe rings exert a uniform pressure in all directions on the walls of thecylinder in order that the wear may be as uniform as possible and thatthe cylinder walls shall not -beworn out of a true circular shape.

By my process or method, pistonrings may be produced which have theirinside and outside walls substantially parallel or concentric, and whichin their natural or expanded position assume an approximately ellipticalform with walls on 'each side of the slot having curves of varyingradii. Rings when so made assume a truly circular form when closed.

The reason why rings made by my method have walls with curves of varyingradii on' each side of the slot is as follows :The rings are slotted byremoving a portion of the ring varying according to the tension desired.The rings are then closed" in to 0 bring the ends together at the slot24:. lln closing in the rings with my flexible fixtures as shown in Fig.4, the-rings naturally bend 110 or spring in the greatest amount at apoint directly opposite the slot 24 as that is the point at which thegreatest leverage is exerted. The bending of the walls of the ring isgradually lessened on either side of a point opposite the slot 24: as weapproach the slot and to points a short distance either side of theslot. At these points no bending takes place.

After the rings are closed in as described, the rings are machinedinside .and out to true circles. When allowed to expand after machiningand to their natural condition, it is found that the curvature of thewalls will have the greater radii where they were'bent the most, theradii gradually decreasing to the points nearest the slot where nobending took place, and at these pointsthe radii of the curves equalthe'radii of the circles of the ring when closed.

In the drawings illustrating the practice of my method and in thedescription thereof, fixtures or devices are shown 'for machining aplurality of rings at some of the steps 1n my method, but it will beunderstood, however, that my method'is appllcable as well to ringswhen'machined singly.

I do not confine the practice of my method of making piston rings to theuse of the particular form of fixtures or de v1ces 1llu strated herein,any form of flexible closing-1n device may be used that will produce.the desired result; and the same is true of the devices for machiningthe outside and ins1de of the rings. This application is dlrectedarticularly to the method or process herein illustrated and described.

What I claim is 1. The method of making piston rings, which consists inslotting a close-d ring on its opposite sides to split the same and formends capable of overlapplng, applying pressure to the outercircumference of the spllt ring to close the same, applying pressure tothe sides of the ring thus closed to retain it in its closed position,removing the circumferential pressure, treating the outer circumferenceto render it a true circle whlle held in its closed position by saidside pressure, placing the ring thus treated W thin a holder whose innercircumference is concentric with the circumference of the rlng, allowingthe ring to expand into contact with said holder, securing the ringwithin said holder in fixed relation'thereto by pressure applied to thesides of the ring, and treating the inner circumference of the rmg torender it concentric with theouter circumference thereof.

2. The method of making piston rings, which consists in slotting aclosed ring on its opposite sides to split the same and form endscapable of overlapplng, applying pressure to the outer circumference ofthe split ring to close the same, applying pressure to the sides of thering thus closed to retain it in its closed position, removing thecircumferential pressure, treating the outer circumference to render ita true circle while held in its closed position by said side pressure,placing the ring thus treated within a holder whose inner circumferenceis concentrio with the circumference of the ring, a1- lowing the ringtoexpand into contact with said holder, securing the ring within saidholder in fixed relation thereto by pressure applied to the sides of thering, treating the innercircumference of the ring to render itconcentric with the outer circumference thereof, removing the ringfromthe said holder, again contracting the ring to close the same, securingit in its closed position by side pressure, removing the circumferentialpressure, and machining the outer circumference of the ring.

3. The method of making piston rings, which consists in contracting asplit ring into its closed position, holding the split ring in itsclosedpositionfby pressure applied to the sides of the ring, machining theouter circumference of the closed split ring to a true circle, expandingandcontracting the ring thus treated and securing it in its closedposition by pressure applied to the sides thereof, machining the innercircumference of the ring to circular form concentric with the outercircumference thereof, expanding and contracting the ring thus treated,and again machining the outer circumference of the ring.

4:. The method of making piston rings, which consists in contracting asplitring into its closed position, machining the outer surface of theclosed ring to a true circle, expanding and then closing the ring thustreated and machining the innersurface thereof to a true circleconcentric with the outer circumference thereof, expanding and thenclosing the ring thus treated and machining the outer circumferencethereof into circular form concentric with the inner circumferencethereof.

5. The method of making piston rings, which consists in contracting asplit ring into its closed position, machining the outer surface of theclosed ring to a true circle, expanding and then closing the ring thustreated and machining the inner surface thereof to a true circleconcentric with the outer circumference thereof.

6.-The method of making piston rings, which consists in contracting asplit ring into its closed position by pressure applied to the outercircumference of said ring and capable of yielding under the influenceof a counter pressure exerted against it by movement of the metal of thering, applying pressure to the sides of the ring to hold it in itsclosed position and so as to leave the outer circumference thereof freeto be machined after the circumferential pressure has been removed,removing said circumferential pressure and machining the outercircumference of the closed ring to practically true circular form,removing said lateral pressure, expanding the ring, closing it again,applying pressure to the sides of the closed ring to hold it in itsclosed position and so as to leave the inner circumference free to bemachined, and machining the inner circumference to practically truecircular form concentric with the outer circumference of said ring.

7. The method of making piston rings, which consists in contracting asplit ring into its closed position, applying pressure to the sides ofthe ring to hold it in its closed position and so as to leave onecircumferential surface free to be machined, machining saidcircumferential surfaceto practically true circular form, removing thelateral pressure and again a'pplyin it to the sides of the ring to holdthe ring 1n its closed position and soas to leave the othercircumferential surface' 'f'ree to be machined, and machining thelast-mentioned circumferential surface to practically true circular formconcentric With the first-mentioned circumferential surface.

8. The method of making piston rings which consists in machining theedges of the rings to size, removing the scale from the outside'of therings, slotting them, closing them in with flexible fixtures, machiningthem so the peripherv is round When contracted, again closing them in tomachine and remove the scale from. the inside so the inside surface ofthe rings will be concentric with the outside, again'closing-in therings With flexible fixtures to finally finish their outside surfaces sothat when completed the rings will be round When closed-in andelliptical When open to their natural position.

'9. The method of making piston rings which consists of removing thescale from the edges and outside of the rings, slotting them andthereafter machining them outside, inside and again outside in the ordernamed and closing said rings before the outside machining operations, bymeans Which permit the rings to contract naturally Without undue localrestraint and so they will be round when closed-in and elliptical whenopen, With the long axis of the ellipse at right angles to the slot.

10. The method of making piston rings, Which consists in contractinginto its closed position a ring blank having a substantially Wide slotand possessing substantially no spring tension, so as to impart to saidslotted ring blank a maximum spring tension, holding said slotted ringblank in its closed position so as to leave first one and then the otherof its circumferential surfaces free to be machined While the slottedring blank is under said maximum spring tension, and machining saidcircumferential surfaces to true circular form concentric With eachother in the closed-in position of the ring and capable RICHARD P.ELLIOTT.

